Closures comprising metallic shells having circular top panels and cylindrical skirts extending downwardly from the peripheral edges of the top panels and molded liners disposed on the inside of the panels have gained widespread acceptance for use with containers, such as bottles, having a threaded peripheral surface at their neck portion. It is important that in such closures, a circumferentially extending annular groove should be formed at a specified point in the upper portion of the skirt of the shell, as will be explained below with reference to the drawings.
Generally, the container closures are produced by fabricating a shell of a desired shape, supplying a liner material to the inside of a top panel portion of the shell and molding the liner material. Molding of the liner material is effected by placing an inverted shell on an anvil and where the liner material has been previously supplied to the inside of its top panel. A molding tool is then lowered in a perpendicular direction into the shell.
A molding tool that is widely used comprises a central molding member composed of a center punch, an annular bushing and a shell positioning sleeve disposed externally of the central molding member, all as disclosed, for example, in Japanese Laid-Open Patent Publication No. 65184/1978. Such a conventional molding tool, however, gives rise to various problems as will be described in detail hereinbelow with reference to the accompanying drawings. For example, the positioning action of the positioning sleeve upon the shell is too slow. Moreover, the positioning sleeve is likely to contact or abut the annular groove of the shell to cause undesirable deformation of the annular groove and often the liner material cannot be molded into the desired shape.